Oxidoreductases are enzymes concerned with biological oxidation and reduction, and therefore with respiration and fermentation processes. The class of oxidoreductases includes oxidases, laccases (1.10.3), peroxidases (1.11.1.7) and oxygenases. The use of peroxidase and laccase enzymes in a process for the oxidation of a wide variety of substrates is already known. For example, the use of peroxidases for bleaching fabrics during washing has been suggested in EP-A-424 398 (Novo Nordisk). WO-A-91/05839 (Novo Nordisk) describes the inhibition of dye transfer during the wash by means of peroxidase or an enzyme exhibiting oxidase activity on phenolic compounds. The compositions are said to bleach any dissolved textile dye so that no dye can redeposit upon the fabric. U.S. Pat. No. 4,690,895 (Repligen Corporation) discloses the use of a specific peroxidase, namely ligninase, to bleach or decolorize kraft pulp for the production of paper.
It is also known that the activity of oxidoreductases, especially peroxidases, may be increased by the addition of certain organic compounds. The use of such activated enzyme systems for various purposes has also been described, for instance for inhibiting dye transfer in a washing process. The above mentioned WO-A-91/05839 (Novo Nordisk) also describes that the addition of another oxidisable substrate may enhance the enzyme activity. Examples of such oxidisable substrates or "enhancers" are certain phenolic compounds, e.g. 2,4-dichlorophenol.
In three subsequent patent applications (WO-A-94/12619, WO-A-94/12620 and WO-A-94/12621, all Novo Nordisk) it is disclosed that the action of peroxidase in such anti dye-transfer compositions may be enhanced by the addition of a number of aromatic compounds, of which 2,2'-azo-bis-(3-ethylbenzo-thiazoline-6-sulphonate) or ABTS appears to be the preferred compound. However, some of these aromatic compounds may not be attractive as ingredients of detergent compositions for economical or environmental reasons. Furthermore, some of these enhancers like ABTS are, in their oxidised form, dyestuffs themselves. This has the disadvantage that the washed fabrics may be coloured by residual amounts of oxidised ABTS.
WO-A-97/06244 (Ciba) discloses various other compounds as enhancers for peroxidase and laccase systems, such as substituted naphtols, barbituric acids, and substituted coumarins.
Thus, although some of these approaches have been successful to a certain extent, there is still a need for alternative or improved enhancers for the activity of an oxidoreductases. In particular, there is a need for effective enzymatic bleach compositions. It is therefor an object of the present invention to provide such effective alternative or improved oxidoreductase enhancers and enzymatic bleach compositions containing them.
We have now surprisingly found that these and other objects can be achieved by new enzyme enhancers of the invention.